/**
 * 获取系统当前时间
 * @returns 字符串
 */
function now(){
    function check(n){
        return n>9?n:'0'+n
    }
    var  now=new Date();
    var year=now.getFullYear();
    var  month=check(now.getMonth()+1)
   
    
    var  day=check(now.getDate());
    
    
    var hour=check(now.getHours());
    
    var minute=check(now.getMinutes());
    
    var  second=check(now.getSeconds());
   
   
    return `${year}-${month}-${day} ${hour}:${minute}:${second}`;
}
// var str=now();
// document.write(str);
